Anonymous password-based key exchange with low resources consumption and better user-friendliness

Anonymous password authenticated key exchange (APAKE) protocols allow the server to authenticate its clients without revealing their identities. In this paper, we first construct a basic protocol SAPAKE by using the homomorphic encryption scheme and an auxiliary memory device. Compared with the previous ones, SAPAKE is more suitable for those privacy-sensitive applications (e.g., cloud computing) where reducing server payload and improving user experience are both essential. Furthermore, we refine SAPAKE by removing the use of the memory device to gain an enhanced extension SAPAKE+ without increasing the resources consumption. SAPAKE+ achieves better user-friendliness than SAPAKE while it requires publishing more public parameters. Both of our protocols are practical due to their low (computation and communication) resources consumption and better user-friendliness, and achieve provable security in the random oracle model.